The Cat's Eye Nebula is a planetary nebula that forms when a dying star slowly gives off its outer gas layers. Scientists think the star released its gases in pulses every 1,500-years. These pulses of gas made huge dust shells surrounding the star. These dust shells made layers of rings like an onion around the dying star. In this view of the Cat's Eye Nebula taken by the Hubble Telescope, you can see the rings, like an onion cut in half.